Conferva nummuloides Eng. Bot. pl., 2287, not Dillwyn.
Meloseira borreri Grev.
Lysigonium nummuloides (Lyngb., Kuetz.) O'Meara = Gaillonella nummuloides (Dillw.) Bory. See O'Meara, p. 248.
Marine and brackish. Long Island Sound and coast of New Jersey.
Pl. 1, Fig. 7.
LYSIGONIUM VARIANS (AG.) DE TONI
Frustules cylindrical, in long filaments, slightly constricted on each side of the suture; puncta in oblique rows in zone view. Valves 15-35 µ in diam. (De Toni), sub-plane, with fine puncta in lines radiating from the centre. Under medium magnification the frustules appear smooth. Very variable in size.
Meloseira varians Ag.
Fresh water. Common in ditches and springs.
Pl. 1, Figs. 18 and 19.
(hyalos, transparent, and discus, a disc)
Frustules spheroidal; valve with a flattened, irregularly punctate umbilicus from which proceed radiating or decussating lines of fine puncta.
ANALYSIS OF SPECIES
| Valves divided into sectors | stelliger |
| Valves not divided but interrupted by short dark lines at intervals | radiatus |
| Valves with very fine puncta | scoticus |
HYALODISCUS STELLIGER BAIL.
Valve with puncta in oblique decussating rows which, by reason of the difference in obliquity, form numerous sectors. Umbilicus irregular, with scattered, coarse puncta. Margin wide, striated.
Podosira maculata Wm. Sm.
Blue clay. Not common.
Pl. 1, Fig. 22.
HYALODISCUS RADIATUS VAR. ARCTICA GRUN.
Valve with radiating puncta from a rather small umbilicus, the rays interspersed with short, dark lines, having the appearance of spines, at irregular intervals. Margin broad, striated.
Pyxidicula radiata O'Meara.
The Philadelphia form corresponds exactly to Grunow's variety which has closer puncta than the type form.
Blue clay. Rather rare.
Pl. 1, Fig. 21.
HYALODISCUS SCOTICUS (KUETZ.) GRUN.
Valve small, with puncta about 24 in 10 µ, appearing hyaline.
De Toni remarks that it resembles a small form of H. subtilis which occurs north and south of our limits and is yet likely to be recorded.
Cyclotella scotica Kuetz.
Podosira hormoides Wm. Sm.
Blue clay. Not rare.
Pl. 1, Fig. 20.
Endochrome in the form of four flaps or patches bound together about a common pyrenoid. In H. subtilis numerous rod-shaped chromatophores lie in a row and are not bound in the centre (Mereschkowsky).
(stephanos, a crown, and pyxis, a kind of vase or box)
Frustules ellipsoidal, concatenate; valves tumid, of unequal convexity, coarsely areolate, the cells in rows parallel to the longitudinal axis, not radiate, with stray spines or teeth placed concentrically more or less near the margin.
According to Karsten the chromatophores are round or angular discs which lie near the connective zone.
STEPHANOPYXIS TURRIS (GREV.) RALFS
Valve cylindrical, with a crown of stout spines less than the diameter of the valve near the margin. Cells hexagonal, about 2 in 10 µ, sometimes punctate. The valve having the greater convexity has the larger spines, though usually less of them.
Creswellia turris Grev. (Gregory, Diat. of the Clyde, T. R. S. E., vol. 21, part 4, p. 66.)
Stephanopyxis appendiculata Ehr.?
Creswellia is incorrectly based, as stated by Ralfs, on the concatenation of the valves which was not noticed by Ehrenberg in the fossil forms. It had been suggested by Kuetzing in Systema Algarum (p. 126).
Blue clay. Port Penn and Smith's Island.
Pl. 2, Figs. 1 and 2.
STEPHANOPYXIS CORONA (EHR.) GRUN.
Valve larger than in turris, sub-globose, coarsely areolate cells, 4-5 in 10 µ. One valve furnished with a crown of teeth shaped like the letter T and united at the top into a ring above the margin of the valve; the other valve with long spines more or less concentrically arranged.
Blue clay. Not common. Fossil in the Nottingham deposit.
Pl. 2, Fig. 3.
Note.—The diatomaceous deposit, so often called "Bermuda" or "Bermuda tripoli," especially by foreign writers, is in reality the Miocene stratum extending for miles along the Patuxent River near the village of Nottingham, Md. The author is perfectly familiar with the location, having made large collections there. The mistake in the name is due to the fact that Prof. Bailey received material from Mr. Tuomey marked "Bermuda Hundred," which is located near Petersburg, Va. Attempts have been made to find material there and while there is an earth containing Miocene diatoms at Petersburg, it does not exactly correspond to the material sent to Ehrenberg by Bailey, who was in doubt as to the locality. The Bermuda Islands are of coral formation and have no deposits of diatomaceous earth.
(dim. of pyxis, a box)
Frustules globular, solitary or in short fasciæ. Valve more or less hemispherical, areolate, destitute of spines.
PYXIDICULA CRUCIATA EHR.
Valve hemispherical, with large, hexagonal cells. An inner stratum is finely punctate.
Blue clay. Walnut St. Bridge. Rare.
Pl. 38, Fig. 8.
This form is not usually described as having punctate areolæ, but it does not apparently differ from other forms of Pyxidicula of Ehrenberg as described by Kuetzing (Species Algarum, pp. 21-23), including P. areolata. In fact, it differs from Stephanopyxis, which is also sometimes punctate, only in the absence of spines. In fossil deposits the absence of an easily detached stratum is not significant. The difference, except in size, between it and P. mediterranea Grun. (V. H. S., Pl. 95, Figs. 15 and 16), I am unable to determine.
Although many species of Meloseira are fresh-water, the habitat of the group Meloseirinæ is, in general, marine. It more nearly coincides in structure and development with other algæ not diatomaceous, the siliceous envelope constituting its most distinctive feature. As we proceed in the classification, the structure both of the frustule and contents becomes more complicated.
(b) COSCINODISCINÆ
1. Cyclotella.—Valve with two concentric divisions of different structure, one a wide border and the other a central surface.
2. Coscinodiscus.—Valve areolate or punctate, with a narrow border of the same structure.
(cyclos, a circle)
Frustules single or geminate, cylindrical, short, in zone view rectangular or with undulating sides. Valve usually with smooth or punctate striæ, centre sometimes bullose, smooth, or with granules scattered or radiating.
Chromatophores numerous along the valves (Pfitzer).
CYCLOTELLA STRIATA (KUETZ.) GRUN.
Valve 30-80 µ in diam., with coarse striæ, 7-12 in 10 µ, centre coarsely punctate and bullose.
Coscinodiscus striatus Kuetz.
Cyclotella dallasiana Wm. Sm.
Common in the blue clay.
Pl. 2, Fig. 9.
CYCLOTELLA MENEGHINIANA KUETZ.
Frustule in zone view rectangular, undulated; valve, 10-20 µ in diam., marginal striæ robust and transversely punctate, centre radiately punctate.
Cyclotella kuetzingiana Wm. Sm. (not Thwaites).
Crum Creek.
Pl. 2, Fig. 8.
CYCLOTELLA MENEGHINIANA, VAR. STELLIGERA CL. AND GRUN.
Differs from the type in the coarse radiating lines at the centre.
Broomall Lake, Media.
Pl. 2, Fig. 4.
CYCLOTELLA MENEGHINIANA, VAR. STELLULIFERA CL. AND GRUN.
As in type but with the central rays granulate.
Broomall Lake, Media.
Pl. 2, Fig. 12.
CYCLOTELLA STYLORUM (BR.?) V. H.
Margin striated, the alternate striæ thickened near the border, producing an appearance of subquadrate cells. Centre faintly granulate, the outer border of which is encircled by 10-12 puncta, each of which is surrounded by a small hyaline space.
Blue clay. Rare.
Van Heurck gives this form doubtfully as a variety of striata, while De Toni makes it synonymous with it. Van Heurck's figure is not that of Brightwell, but as the specimen above described is, I believe, exactly the same as Van Heurck's, I retain his name.
Pl. 2, Fig. 10.
CYCLOTELLA COMTA (EHR.) KUETZ.
Valve with marginal striæ well marked, each third or fourth costa more robust than the others. Central part finely striated, the striæ punctate, radiating.
Fresh water.
Pl. 2, Fig. 7.
The form here figured is probably the variety radiosa Grun. and is from a New England specimen. It is quite likely to occur in this locality.
CYCLOTELLA OPERCULATA (AG.) KUETZ.
Frustules in zone view undulated. Angles rounded. Marginal costæ alternating with minute spines; centre nearly smooth, depressed, convex or flexuose.
Fresh water.
Pl. 2, Figs. 5 and 6.
The figure is drawn from a specimen from Boston, Mass., H. L. Smith Type Slide No. 107, marked equivalent to C. minutula Wm. Sm.
CYCLOTELLA ANTIQUA WM. SM.
Marginal costæ alternating with thick puncta; centre finely granulate with subtriangular elevations. Frustules in zone view rectangular.
Blue clay.
Pl. 2, Fig. 11.
The form corresponds to the original specimens of Wm. Smith in the deposit of Stavenger, Norway.
The genus Cyclotella comprises about seventy specific names, many of which may be referred to other genera, while some of Ehrenberg's are incapable of verification on account of the small size of the figures and the lack of sufficient description. About half of the forms are marine. The fresh-water species are usually found living in more or less stagnant water or in pools contaminated with drainage, being an exception to the general rule that diatoms are more abundant in water free from deleterious matter.
(coscinon, a sieve, and discus)
Frustules solitary, cylindrical, compressed; valve circular or elliptical; surface flat or sometimes convex near the border; markings more or less angular, radiating, sometimes fasciculate; border usually well defined. Central space, if present, hyaline, sometimes surrounded with a rosette of large cells.
Chromatophores round, angular or irregular discs usually without pyrenoids (Karsten).
Rattray's classification is here followed, so far as it refers to our species.
Excentrici.—Valves circular; central space absent; markings angular, in oblique, decussating rows.
Lineati.—Central space absent; markings angular, oblique decussating rows straight.
Fasciculati.—Markings fasciculate, or sometimes only near the border.
Radiati.—Markings rounded or angular, more or less radiate.
Elaborati.—Valves elliptical, markings rounded.
EXCENTRICI
COSCINODISCUS EXCENTRICUS EHR.
Valve with a hyaline excentric space from which proceed, usually in six directions, rows of polygonal markings decreasing toward the narrow, coarsely striated border, the rows appearing convex toward the centre. Apiculi at unequal distances apart. Quite variable in size.
Common in the blue clay and along the coast.
Pl. 2, Figs. 14 and 20.
Fig. 20 is probably var. perpusilla Grun. (Diat. Fr. Jos. L., Pl. 4 (D), Fig. 7).
LINEATI
COSCINODISCUS LINEATUS EHR.
Valve circular, markings hexagonal, cells in parallel rows. Border narrow, cellular.
Blue clay and Atlantic coast. Not common.
Pl. 3, Fig. 8.
FASCICULATI
COSCINODISCUS NITIDUS GREG.
Valve flat, markings rounded, distant, radiate, decreasing toward the border which is coarsely striate. Quite variable in size and in the distance between the markings.
Blue clay and Atlantic coast. Common.
Pl. 2, Fig. 18.
COSCINODISCUS NITIDULUS GRUN.
Valve usually not quite circular; markings smaller than in nitidus and fasciculate near the border.
Blue clay.
Pl. 2, Fig. 19.
Various intermediate forms between nitidus and nitidulus occur.
COSCINODISCUS SUBTILIS EHR.
Markings polygonal, irregular at the centre, but forming numerous fasciculi radiating toward the border, the rows parallel to the central row of each fasciculus. Border narrow with fine striæ; apiculi often present between the fasciculi.
Blue clay and along the coast. Very common in the water supply of Philadelphia and Camden, where the diameter seldom exceeds 40 µ and the markings on the semi-radius are 10 in 10 µ.
Pl. 2, Fig. 17.
COSCINODISCUS DENARIUS SCHMIDT
Markings larger than in C. subtilis, equal, forming usually ten fasciculi, each beginning near the semi-radius and containing ten parallel rows of granules.
Common in the blue clay and sparingly along the coast.
Pl. 2, Fig. 13.
Forms are found intermediate between C. subtilis and C. denarius, as shown in Fig. 15.
COSCINODISCUS POLYACANTHUS GRUN.
Markings angular, 10 in 10 µ, decreasing toward the border, fasciculate. Apiculi large, twelve or more, usually inserted at the middle of each fasciculus, and extending into the interior of the cell. The apiculi in outline resemble the heads of horse-shoe nails, and are seen with difficulty except when the valve is examined from the inner side. Border narrow, striated. Diam. 70 µ.
Pensauken, N. J., artesian well.
Pl. 38, Fig. 5.
Rattray's description of C. polyacanthus var. intermedia Grun., from Cape Wankarema, Siberia, gives the diam. as 60 µ, and there are about 7 markings by actual count in 10 µ in Grunow's figure (Diat. Fr. Jos. Land, Pl. 3 (C), Fig. 25). The apiculi are more numerous, but there appears to be little doubt of the general similarity. The Philadelphia form is abundant in the Pensauken well deposit at a depth of 33 ft. The apiculi become quite distinct in slides stained with silver nitrate by Mr. F. J. Keeley; they are distinct from small apiculi sometimes evident between the fasciculi. The specimens in the Pensauken deposit are mingled with other forms which cannot be distinguished from C. subtilis. Whether the two are identical, I am unable to determine. Rattray (Rev. Cos., p. 47) refers to H. L. Smith's Type Slide No. 100, from rice-field mud, Savannah, Ga., as C. subtilis. In Smith's slide, in my possession, a number of the forms show faint outlines of the large apiculi and are otherwise exactly like C. polyacanthus.
RADIATI
COSCINODISCUS VELATUS EHR.
Markings angular, decreasing slightly toward the coarsely striated border, covered with fine puncta.
Blue clay.
Pl. 3, Fig. 2.
COSCINODISCUS MARGINATUS EHR.
Markings rounded, large, decreasing toward the broad border, which is coarsely marked with distant striæ. The cells are punctate.
Common in the blue clay.
Pl. 3, Fig. 9.
In the fossil forms the puncta are not evident, hence the species is usually described as not punctate.
COSCINODISCUS RADIATUS EHR.
Markings polygonal, slightly decreasing toward the border where they are much smaller; border well marked, striate. Quite variable in size.
Common in the blue clay and along the coast.
Pl. 3, Fig. 11. Fig. 1 is probably a smaller form.
COSCINODISCUS SUBAULACODISCOIDALIS RATTR.
Markings small, decreasing toward the border in somewhat fasciculate rows. About one-third the distance from the border are five (Rattray finds six) well-marked apiculi somewhat resembling those of Aulacodiscus. Border narrow, hyaline.
Rare in the lower stratum of the blue clay.
Pl. 3, Fig. 4.
COSCINODISCUS ARGUS EHR.
Markings angular with central dots, increasing from the centre toward the border, where they are smaller.
Blue clay.
Pl. 3, Fig. 7 (a small form).
COSCINODISCUS BIANGULATUS SCHMIDT
Central space and rosette absent, markings large, angular, not punctate, with large central papillæ, decreasing toward the border. Border wide, coarsely marked with rows of granules, and with two indentations on the inner side distant from each other about two-thirds of the diameter.
Blue clay.
Pl. 3, Fig. 3.
Distinguished from Coscinodiscus asteromphalus var. omphalantha Grun., which also has two constrictions, by the absence of punctate markings.
COSCINODISCUS ASTEROMPHALUS EHR.
Central space small, surrounded by a rosette of large polygonal cells from which radiate hexagonal cells, increasing about half way toward the border and then slightly decreasing. Cells punctate.
Blue clay.
Pl. 2, Fig. 16; Pl. 40, Fig. 12.
COSCINODISCUS ASTEROMPHALUS VAR. OMPHALANTHA (EHR.) GRUN.
Central space absent, rosette evident. Markings 2½ in 10 µ, somewhat smaller near the rosette and decreasing near the border, which is constricted in two places, as in C. biangulatus.
Blue clay.
Pl. 38, Fig. 10.
COSCINODISCUS OCULUS-IRIDIS EHR.
Central space and rosette distinct; markings polygonal, not punctate, with large papillæ, smaller near the rosette, increasing toward the semi-radius, and then decreasing to the striated border which is comparatively narrow.
Blue clay and Atlantic coast.
Pl. 3, Fig. 10.
ELABORATI
COSCINODISCUS LEWISIANUS GREV.
Valves elliptical, major axis a little more than twice the minor. From a point, usually near one side, radiate rows of granules in lines nearly parallel to the major axis. Border broad, with distinct striæ.
Great Sedge Island, N. J. (artesian well), and in outcrops later than the Miocene, where it is usually found.
Pl. 3, Fig. 5.
ACTINOPTYCHINÆ
Valves divided into sectors alternately elevated and depressed.
(1) Actinoptychus.—Sectors plane.
(2) Polymyxus.—Sectors convex.
(actis, a ray, and ptyx, a fold)
Frustule cylindrical, less in length than the diameter, in zone view undulated. Valve divided into six or more sectors alternately raised and depressed, areolate and punctate, varying in the alternate divisions. The areolation is confined to the outer layer of the valve while the punctation is usually on an inner valve often found detached. Processes on the border, three or more. Umbilicus circular or angular, hyaline.
ANALYSIS OF SPECIES
| Sectors, six | undulatus |
| Sectors, eight or more, cellular | heliopelta |
| Sectors, fourteen, punctate | vulgaris |
ACTINOPTYCHUS UNDULATUS (KUETZ.) RALFS
Valve areolate and punctate in quincunx, divided into six equal sectors, alternately elevated or depressed, their areolations appearing different. Margin well defined. Umbilicus smooth, hexagonal. Processes three, sometimes six, inserted within the margin of each alternate division. Very variable in size and appearance.
This is the Actinocyclus of Bailey, figured and described in Amer. Jour. Science, 1842, p. 93, Pl. 2, Fig. 11, but not named. Kuetzing describes and names it and refers to Bailey.
Actinoptychus omphalopelta Ehr.
Actinoptychus cellulosa Ehr., H. L. Smith Sp. Typ., 384.
Quite common in marine and brackish water and in the blue clay.
Pl. 4, Figs. 1, 2, 4 and 6.
ACTINOPTYCHUS VULGARIS VAR. INTERRUPTA N. VAR.
Valve with fourteen sectors, the alternate ones divided by a smooth lanceolate space for about one-half the radius, forming with the smooth, circular umbilicus a seven pointed star. The sectors thus divided have coarser puncta in quincunx than the other sectors, ending in a smooth area near the margin, and also larger black puncta scattered from the centre to the semi-radius.
Near A. vulgaris var. neogradensis Pant.
Blue clay. Not common.
Pl. 4, Fig. 5.
ACTINOPTYCHUS HELIOPELTA GRUN. VAR.?
Valve circular, sectors, eight, umbilicus circular, without rays; border wide, cellular, with distinct rays. Inserted at a distance within the inner edge of the border are large processes, one on each of four alternate sectors, and two on each of the others. The sectors are cellulate and punctate.
Near A. heliopelta var. versicolor Brun., which, however, in the specimen in my collection from Atlantic City (artesian well), has a greater number of processes and they are situated on the edge of the border.
Outcrop at Buckshutem, N. J. Rare.
Pl. 4, Fig. 3.
It has been quite well determined, I think, that the typical forms of A. heliopelta occur at the base of the Miocene. At Rock Hall, Md., on the eastern shore of Chesapeake Bay, at a depth of from 21 to 130 ft., and at Wildwood, N. J., at a depth of from 78 to 179 ft., diatomaceous beds occur considered by Mr. Lewis Woolman (Geol. Surv. of N. J., 1898, pp. 116-121) "as synchronous in age," the former being deposited in the Delaware River Delta and the latter in the Chesapeake in post-miocene times. In each of these beds a small form of A. heliopelta is rarely found. The material at Buckshutem is post-miocene, and the form here figured shows a marked variation from the Miocene species and a gradual approach toward A. undulatus.
Valve circular, usually divided into fourteen sectors which are on the same plane at the centre, but the alternate ones are elevated into mammillated projections terminated by small processes on the margin. Zone view rectangular with undulations subconical, terminated by the processes.
POLYMYXUS CORONALIS L. W. BAIL.
Central space hyaline, rounded or slightly stellate, from which radiate rows of fine puncta in quincunx, shown in the figure only on the alternate elevations, the depressed interspaces being out of focus. The mammillæ are stated by Bailey to vary from six to ten.
Very rare in the blue clay (Walnut St. Bridge). Occurs also in the Wildwood deposit (Bull. Torrey Bot. Club, 1895, p. 261).
Pl. 4, Fig. 7, and Pl. 5, Fig. 2.
Aulacodiscinæ.—Valves with mammiform elevations near the border surmounted by nipple-like processes.
AULACODISCUS—THE ONLY GENUS AS ABOVE
Eupodiscinæ.—Valves with ocelli.
(1) Actinocyclus.—Valve with one small ocellus; striæ radial.
(2) Eupodiscus.—Valve with one or more ocelli; striæ not radial.
(3) Auliscus.—Valve with large, elevated ocelli. Central area hyaline. Markings granular and costate.
(4) Pseudauliscus.—Valve with radiating granules. No central space.
(aulax, a furrow, and discus)
Valve usually circular, plane or with an elevated zone, frequently inflated beneath the processes; central space irregular or rounded, sometimes absent; markings granular, radial, sometimes in a reticulum.
The genus comprises more than one hundred species most of which are fossil, and is represented in this locality by a single form, A. argus, included by Rattray in his section "Retiformes," distinguished by the presence of a reticulum.
AULACODISCUS ARGUS (EHR.) SCHMIDT
Frustule in zone view elliptical. Valve circular, 125-190 µ in diam., closely covered with two kinds of markings, one, a mesh of large, radiating, angular cells, the outer plate, and the other, radiating rows of circular granules with hyaline spaces intervening and closer near the border, forming the inner plate which can occasionally be seen detached. Central space absent. The walls of the angular cells are crossed with fine lines and are probably composed of granules compressed so closely as to produce partial opacity, the depth of which depends in a measure not only on the superposition of the two plates, but on the relative closeness and thickness of the cell-walls. In a fully-developed specimen the effect is to produce more or less triangular cells containing three or four granules. In some cases the opacity is so great as to render detail invisible.
In the figure the valve is supposed to be divided into three sectors, illustrating at "a" the lower plate, at "c" the combination of the upper and lower plates, and in the other sector the cellular mesh of the upper plate. Processes, usually three, quite robust and inserted at from one-fourth to one-fifth the length of the radius from the border which is striated on the inner side. A form with four processes is found in the lower blue clay.
Tripodiscus argus Ehr.
Eupodiscus argus (Ehr.) Wm. Sm.
Not uncommon in the blue clay.
Pl. 4, Fig. 8.
(actis, a ray, and cyclos)
Valve circular or elliptical; surface flat at the centre, sloping toward the border. Central space usually evident, rounded or irregular. Markings rounded, granular, punctiform, in radial, or nearly radial, rows, sometimes fasciculate. A nodule, more or less evident, is found near the border which is usually striate.
Chromatophores round discs or granules.
ANALYSIS OF SPECIES
| Valve circular, rows radial, hyaline lines at the border | barkleyi |
| Valve circular, rows fasciculate | moniliformis |
| Valve elliptical | ellipticus |
The nodule is generally supposed to be a thickening of the cell-wall, and, in the opinion of Rattray, a projection outward, but "whether there may not be at the same time a slight inward protuberance is difficult to determine," though, as a rule, he seems to "think there is not."
ACTINOCYCLUS BARKLEYI VAR. AGGREGATA RATTR.
Surface flat from centre to semi-radius. Central space irregular, sometimes with a few scattered granules. Markings round with central dots distinct, about 7 at the centre, decreasing in straight radial rows to 12 in 10 µ at the border, where they form moniliform striæ. Border narrow with striæ about 16 in 10 µ. Hyaline interspaces at the origin of the shorter rows, but not at equal intervals. At the border, linear hyaline spaces occur at somewhat irregular intervals between the moniliform striæ owing to the termination of certain radial rows before they reach the circumference. Nodule small, from one-seventh to one-fourth the radius from the border.
According to Rattray the distinction between A. ralfsii and A. barkleyi is partly in the absence of the zone arrangement of the hyaline spaces in the latter, and to the slight differences in the number of granules. The variety aggregata differs from the type form of barkleyi mainly in the distance of the nodule from the border. I have specimens from the blue clay material at Walnut St. Bridge, and from Smith's Island, in which the distance from the border in one case is, as stated above, quite different from that in the other. In specimens from Morris Cove, Conn., the locality referred to by Rattray, variations occur.
Blue clay.
Pl. 6, Fig. 1.
In the figure the subulate hyaline spaces at the border are, in some instances, wider than usual.
ACTINOCYCLUS MONILIFORMIS RALFS
Surface flat, from centre to about five-sixths of the radius. Central space rounded, with one or more granules. Markings, 8 in 10 µ, round, in radial rows, fasciculate, the oblique transverse rows irregular, very slightly decreasing until near the edge of the flattened zone, and then suddenly decreasing and appearing as decussating lines oblique to the border. Apiculi distinct, interfasciculate within the border. Nodule quite evident, surrounded by a rather wide irregular hyaline space on the margin of the flattened zone in the middle of the fasciculus. Border wide, with striæ about 20 in 10 µ.
Blue clay. Port Penn. Not common.
Pl. 6, Fig. 2.
Equivalent to Actinocyclus ehrenbergii, H. L. S. Type Slide 10.
In a valve from Port Penn, Delaware Bay, two nodules occur nearly opposite each other.
ACTINOCYCLUS ELLIPTICUS VAR. DELAWARENSIS N. VAR.
Valve rhombic-elliptical. Markings somewhat angular, 6 in 10 µ at the centre where they are sub-concentric, thence decreasing in lines radiating more or less toward the border, where they suddenly become punctiform, striæ about 20 in 10 µ. Border equal to one-fifth the radius. A nodule is found on the inner side of the border. Apiculi apparently absent.
The markings are larger than in the Richmond forms which are associated by Rattray with Actinocyclus ellipticus Grun. The form corresponds closely to Witt's Cestodiscus ovalis var.? (Witt, Polierschief. von Archangelsk-Kurojedowo, Pl. 8, Fig. 2), except as to the border. It does not answer to Van Heurck's figure or any other.
Blue clay. Very rare.
Pl. 3, Fig. 6.